Structure and Stability of Cuspy Triaxial Galaxies

kandrup, Henry e . Cuspy三轴星系的结构和稳定性本项目的目标是构建Cuspy椭圆星系和早期型凸起的三轴分布函数（df）。这将涉及经典天体力学、现代非线性动力学和统计力学以及数值算法等技术的整合，例如对Schwartzschild的DF构造技术的修改。它旨在回答这样一个问题：在三轴星系中DF和表面密度分布之间有什么联系，混沌在这种联系中有什么影响，或者表面密度分布是初始条件的遗迹？最近的高分辨率观测表明，许多（也许是大多数）椭圆星系有一个明显的密度尖峰，可能与超大质量黑洞的存在有关；此外，对于顶点不是太陡的星系，通常有证据表明它们与轴对称有适度的偏差。然而，由数值研究证实的理论论点有力地表明，在一个cusy的非轴对称星系中，许多恒星将表现出混沌运动。直到最近，这个领域几乎所有的工作都完全忽视了这种混乱的可能影响。该项目将探索这种混沌对星系结构和演化的物理含义，特别关注确定潜在的可观测特征。需要解决的问题包括：1。把这样的星系建模为与时间无关的统计平衡是合理的吗？或者，我们是否可以预测，在天文有趣的时间尺度上，cuspy非轴对称星系应该表现出系统的进化效应？2. 这些星系对与其他相对邻近星系的存在相关的低振幅引力不规则性有多敏感？3. 这样的星系与附近的星系碰撞或近距离接触时将如何反应？这项工作的大部分涉及到物理学家和应用数学家在过去三十年中发展起来的思想的应用，这些思想在实验室中得到了反复的证实。然而，在星系背景下出现的一个重要新特征是混沌是自洽产生的：在大多数实验室实验中，混沌是由作用于被探测系统的某些外部刺激触发的。当考虑一个星系时，人们面临着这样一种情况，即混沌是由与星系本身的物质相关的引力引起的。本项目由美国国家科学基金会星系外天文学和宇宙学项目（AST/EXC）资助

AST-0070809Kandrup, Henry E.Structure and Stability of Cuspy Triaxial GalaxiesThe goal of this project is to construct triaxial distribution functions (DFs) for cuspy elliptical galaxies and early-type bulges. This will involve the integration of techniques from classical celestial mechanics, modern nonlinear dynamics and statistical mechanics, as well as numerical algorithms, such as modifications to Schwartzschild's technique for DF construction. It aims to answer the question: What is the connection between the DF and the surface density profiles in triaxial galaxies, and what is the influence of chaos in this connection or are the surface density profiles relics of initial conditions?Recent high resolution observations indicate that many (perhaps most) elliptical galaxies have a pronounced density cusp, possibly associated with the presence of a supermassive black hole; in addition, for galaxies where the cusp is not too steep, there is often evidence for moderate deviations from axisymmetry. However, theoretical arguments, corroborated by numerical investigations, suggest strongly that many of the stars in a cuspy, nonaxisymetric galaxy willexhibit chaotic motions. Until very recently, almost all work in this area has completely ignored the possible effects of this chaos. This project will explore the physical implications of this chaos on the structure and evolution of galaxies, with particular focus on determining potentially observable signatures. Questions to be addressed include the following: 1. Is it reasonable to model such galaxies as being in a time-independent statistical equilibrium, or would one anticipate that cuspy nonaxisymmetric galaxies should exhibit systematic evolutionary effects over astronomically interesting time scales? 2. How susceptible are such galaxies towards low amplitude gravitational irregularities associated with the presence of other comparatively nearby galaxies? 3. How will such a galaxy respond to a collision or close encounter with a very nearby galaxy? Much of this work involves applications of ideas which have been developed by physicists and applied mathematicians over the past thirty years and which have been confirmed repeatedly in the laboratory. However, an important new feature arising in the context of galaxies is that the chaos is generated self-consistently: In most laboratory experiments, chaos is triggered by some external stimulus acting on the system being probed. When considering a galaxy one is confronted with a situation where the chaos is induced by the gravity associated with the matter in the galaxy itself. Funding for this project is provided by the NSF program for Extragalactic Astronomy & Cosmology (AST/EXC).***